At last we’ve made it to the end of term. This morning I delivered my last particle physics lecture. Given that it is the last day of the semester I was half-expecting no students would turn up, but in the end I had about 60% attendance. At the end of my lecture there was even a smattering of applause, which I interpreted as meaning that the students were happy that I’d finished.
I thought I would end this module with some topics that I didn’t have time to cover in any detail, but thought the students should know at least something about. These loose ends included:
Renormalization
Grand Unified Theories (GUTS)
Supersymmetry (SUSY)
Particle candidates for Dark Matter
Baryogenesis
I only had time for a superficial treatment of these topics, but felt the class should at least hear the words. There are some very good unanswered research questions under those headings, which I think is an appropriate way to end a final-year module, given that at least some of the class are intending to carry on to further study in physics.
This afternoon we had a colloquium by our PhD student John Ibrahim on the subject of the “Quark‑Gluon Vertex and Confinement of Quarks”. It was a nice talk but it struck me how big the gap was between what I’d been teaching at undergraduate level and the standard that a PhD student has to reach.
Today was also the deadline for Computational Physics projects. I’ll be grading them next week. Even then the term won’t quite be over – there is the small matter of exam marking to be done – but at least I’ve got no more formal teaching to do until September.
Last night on the way home I decided to buy a nice bottle of white wine and put it in the fridge so I could drink it in celebration of the end of term when I get home, with a nice fish supper.
I’ve had these pictures for quite a while and can’t remember where I got them from, but I used to show them in my lectures on Theoretical Particle Physics when I was in Nottingham to illustrate CP-violation and used them in this morning’s lecture at Maynooth.
The following picture by M.C. Escher is called Day and Night:
If you look at it you can see two kinds of symmetry emerging. One is a kind of reflection symmetry about a vertical axis drawn through the centre of the picture that applies to shapes but not to colour. The other is between black and white. But it is obvious that the picture doesn’t display these symmetries separately: to get a picture unchanged from the original you would have to do the mirror reflection and change black to white (and vice-versa).
The mirror reflection in the image can be taken to represent parity (P). Strictly speaking parity refers to a reflection through the origin in 3D rather than a mirror reflection, but it’s just for illustration. We know that a parity symmetry is violated in weak interactions just as it is in the picture.
The other possible symmetry, between black and white can be taken to represent charge-conjugation (C), the operation that converts particles into anti-particles and vice-versa.
While P is not an exact symmetry of weak interactions, it was long thought that the combination of C and P (CP) would be. Actually it isn’t. The story of the discovery of CP-violation is fascinating but I don’t have time to go into it here. It suffices to say that the Escher print also displays CP violation.
First lets do `C’, i.e. convert black to white and vice-versa. The result is:
Now reflect about the vertical mid-line to illustrate `P’:
If `CP’ were an exact symmetry then that image would be identical to the original, which I reproduce here:
You can see, however, that while some elements of the picture do look the same after this combined operation (e.g. the birds), others (e.g. the buildings at the bottom) do not. Although CP is not an exact symmetry of this picture, it is almost (just like it is in particle physics).
So the Easter break is over and I was back to campus today armed with a very long to-do list. I’m pleased to say I’ve ticked all the items off except the last, which was to prepare my lecture for 9am tomorrow. I’ll do that after supper.
I was very tired this morning after doing a bit of gallivanting for a couple of days. Am I too old to be carrying on like that? Yes. Do I intend to stop? No. Although I had a lot to do I didn’t have any lectures or tutorials so I was able to knuckle down and get on with things, interrupted only by an obligatory telecon.
We have four weeks left until the end of lectures for Semester 2. To be precise it’s four weeks minus one Bank Holiday (on Monday 4th May) which makes it 3.8 (working) weeks, but I don’t have lectures on Mondays so this isn’t very relevant to me. My Particle Physics module will continue in the same vein until the end of teaching but Computational Physics changes after this week, with lectures and formal lab sessions ending allowing the students time to do their mini-projects (which they have already started). They will still have access to the labs and be able to consult the demonstrators for help on their projects, though they can work at home (or somewhere else) instead if they prefer.
Other signs of the approaching end of term is that the May Examination timetable has been published, the required papers are being printed, schedules of student presentations are being circulated, and arrangements being made to mark projects.
When teaching is over for the academic year , and before exam marking starts, assuming a whole day of decent weather arrives, I plan to walk from Maynooth into Dublin along the Royal Canal. That’s a distance of 27 km. I do intend to walk the length of the National Famine Way later this year, but I was convinced to do one stage first to see if my knees can take it. The final leg of the Famine Way is from Maynooth to Dublin, which is convenient because if I’m forced to give up I can easily get the bus or train home, as I can if I reach the end.
Now for a quick supper, write my lecture for tomorrow morning, and have an early night!
It’s Sunday 29th March – Palm Sunday in fact – and Friday 3rd April is Good Friday, which is followed by a break of a week for Easter, so I’ve been looking at what I have to do in the four days between Monday and Thursday.
On Tuesday afternoon part of my 3rd Year Computational Physics class will be doing a supervised test in the computer lab. I (foolishly) promised to ensure they would get their grades before Easter, so I’m going to have to mark them straight away. This is a larger group than usual because some students who would normally be in the lab on Thursdays swtiched to Tuesday so they could go on a trip to Armagh. Anyway, this is the third lab test and at least I have graded the first two tests for all groups in time for the arrival of the new ones.
There will be one more of these lab tests after the Easter break but after that the students will be working full-time for 3 weeks or so on mini-projects. That is the part they usually enjoy most and I’m very happy to see that some have already started work.
Then, on Wednesday I have the second class test for my 4th year Particle Physics module. This is the second such test, and it will be held during a tutorial session. This is a pen-and-paper test rather than a coding test to be done in the lab. For such tests I allow students to bring whatever they like on paper but phones, laptops and tablets are banned. This is the easiest way I could think of to avoid students using AI to solve the problems. In previous years I gave take-home assignments for this module, and I still hand out exercise sheets to be gone over in tutorials, but these are for formative purposes only. The summative assessments are the class tests. There will be three of those, which means they will have to endure one more after Easter. In a normal week I would have a Particle lecture on Friday, but that won’t happen because it’s Good Friday and my lectures apparently aren’t good enough to happen on that day.
As well as the Computational Physics lab test and the Particle Physics class test, next I have two lectures, both at 9am – one on Tuesday and one on Thursday – and another lab session on Thursday which is not a test, but a practical session about solving ODEs.
Then it will be the Easter Break. After that, according to my calculations, there will be four more teaching weeks before the examination period. The last day of teaching is May 8th. Between that and the examinations there is a gap of a week during which I will have to mark all the completed Computational Physics project reports, as well as giving some revision classes if there is demand for them.
I am remiss in having forgotten until now to circulate an open letter that has been set up to express support for the high energy physics theory and particle theory communities in the United Kingdom. I signed the letter a few days ago but neglected to circulate it for further signature.
The letter reads:
We the undersigned wish to raise serious concerns about the current cuts to UK high energy particle physics theory grants by signing up to the letter below. The open letter and list of signatories are printed on this page. Individuals who wish to support this initiative may add their name as a signatory by completing the form below. This letter will be sent to Lord Patrick Vallance (Minister of State for Science, Innovation, Research and Nuclear), Liz Kendall (Secretary of State for Science, Innovation and Technology), Chi Onwurah MP (Chair of the UK House of Commons Science, Innovation and Technology Select Committee), and Prof. Sir Ian Chapman (CEO of UKRI).
We are signing this letter to raise serious concerns about the proposed cuts to high energy physics theory and particle theory in the United Kingdom. The UK is a world leader in this area: its historical activity led to the development of the Standard Model of particle physics and the ongoing development of string theory. UK theoretical physicists provide essential input to major international experiments, including the Large Hadron Collider at CERN and next-generation programmes in neutrino physics, gravitational waves, and cosmology, enabling rigorous interpretation of data and the extraction of fundamental insight. The strength of the UK community lies in its intellectual breadth and integration: researchers operate across phenomenology, formal theory, and their interface, and sustained dialogue between these areas underpins the UK’s leading role in global collaborations and internationally recognised research groups. In parallel, UK theorists advance the theoretical foundations of fundamental physics.
These groups and scientists can only operate thanks to critical funding by UK research council funding.
The current apparent scale of the cuts to the Particle Physics, Astronomy and Nuclear Physics area (30% to the overall budget) will result, when rising costs are taken into account, in a much greater than 50% cut in the number of postdoctoral researchers active in these areas in the UK. This will have a devastating effect on the ability of the UK to maintain its leading role in the subject.
Such funding decisions will affect the famously excellent reputation of the UK university sector. It will risk the health of UK physics departments and will therefore damage economic growth in the UK. Many scientists trained in this sector subsequently move into senior positions in technical industries such as machine learning and finance. Theorists at universities play a crucial role in the training and development of the inventors and disruptors of the future.
We urge UK politicians and leaders in the UK funding organisations to carefully consider the implications of the current direction of funding decisions before it is too late and irreparable damage is done to the UK theory community.
You can sign the letter and see a list of existing signatories here.
I searched for a free stock image using “quarks” as a search term and found this photo by Anh Nguyen on Pexels.com.
On most Friday afternoons there is a seminar in the Physics Department at Maynooth University, and I got it into my mind that there was one this afternoon and set aside an hour to attend it. It turns out that there isn’t a seminar so I have time to write a quick blog post before I head to Dublin for a concert.
We’ve (almost) reached the end of Week 3 of the Semester which means we’re about a quarter of the way through the term. Yesterday we did the first Lab Test of four in Computational Physics, which went off without any major problems. The first class test in Particle Physics will be next week and I hope that goes equally well.
Today’s the day students officially received their provisional first semester results. When I arrived at my particle physics lecture this morning the students were discussing their exam marks. Most seemed relatively happy, which is good because this is the final year for most of these students so their grades matter more now than in previous years.
This morning’s lecture was quite amusing. I was discussing electrostatic interactions between quarks in nucleons and in the course of that I asked the class to calculate (2/3)×(-1/3) +(-1/3)×(-1/3)+(-1/3)×(2/3). It took a surprisingly long time to arrive at the right answer! To make matters worse, when I announced the correct answer I got the sign wrong*.
It’s been a long week.
Anyway, next week I’ll be starting on the Dirac Equation, and on the basis of today’s events I wonder about the wisdom of having a lecturer who can’t do minus signs teach relativistic quantum mechanics to students who struggle to do simple arithmetic with fractions!
A neutral pion can decay into two photons. It is therefore not unreasonable to ask the question whether the reverse process – the creation of a neutral pion by colliding two photons – is physically possible and, if not, why not? It is perhaps less reasonable to ask an AI bot these questions. One of my colleagues did just that and found it said “no”, giving the following three answers to the “why not?” question:
I particularly like the second one.
Would anyone like to offer a correct answer through the comments box?
I saw the news today that the Republic of Ireland is now officially an associate member state of the Conseil Européen pour la Recherche Nucléaire, better known as CERN. This has been in the pipeline for a while: I blogged about it here, for example. But today’s the day that Ireland formally joined.
I think this is a very good move for Irish physics, and indeed for Ireland generally. I will, however, repeat a worry that I have expressed previously. There is an important point about CERN membership, however, which I hope is not sidelined. The case for joining CERN made at political levels was largely about the return in terms of the potential in contracts to technology companies based in Ireland from instrumentation and other infrastructure investments. This was also the case for Ireland’s membership of the European Southern Observatory (ESO), which Ireland joined 7 years ago. The same thing is true for involvement in the European Space Agency, which Ireland joined in 1975. These benefits are of course real and valuable and it is entirely right that arguments should involve them.
Looking at CERN membership from a purely scientific point of view, however, the return to Ireland will be negligible unless there is a funding to support scientific exploitation of the facility. That would include funding for academic staff time, and for postgraduate and postdoctoral researchers to build up an active community as well as, e.g., computing facilities. This need not be expensive even relative to the modest cost of associate membership (approximately €1.9M). I would estimate a figure of around half that would be needed to support CERN-based science. I am given to understand that some funds have been made available as part of the joining arrangements, but I don’t know the details.
As I have mentioned before, Ireland’s membership of ESO provides a cautionary tale. The Irish astronomical community was very happy about the decision to join ESO, but that decision was not accompanied by significant funding to exploit the telescopes. Few astronomers have therefore been able to benefit from ESO membership. While there are other benefits of course, the return to science has been extremely limited. The phrase “to spoil a ship for a ha’porth of tar” springs to mind.
Although Ireland joined ESA almost fifty years ago, the same issue applies there. ESA member countries pay into a mandatory science programme which includes, for example, Euclid. However, the Irish Government did not put any resources on the table to allow full participation in the Euclid Consortium. There is Irish involvement in other ESA projects (such as JWST) but this is somewhat piecemeal. There is no funding programme in Ireland dedicated to the scientific exploitation of ESA projects.
Under current arrangements the best bet in Ireland for funding for ESA, ESO or CERN exploitation is via the European Research Council, but to get a grant from that one has to compete with much better developed communities in those areas.
The recent merger of Science Foundation Ireland and the Irish Research Council to form a single entity called Research Ireland could provide an opportunity to correct this shortfall in funding for science exploitation. The reorganization won’t do anything on its own, however: the overall level of public sector research funding will have to increase dramatically from its current level, well below the OECD average. The recent Budget in Ireland for 2026 does include an allocation of €426 million for research under the National Development Plan, but how much of this will find its way into basic research generally and CERN science in particular?
A couple of years ago I posted an item about a measurement of the anomalous magnetic moment of the muon, a quantity usually known as (g-2). At the time this appeared to be in conflict with the predictions of the standard model (SM)of particle physics but the general opinion among experts was that the problem was likely to lie with the calculations rather than the experiment.
If this is too small to read I direct yourself to the salient point, namely that “there is no tension between the SM and experiment at the current level of precision”.
It seems the Standard Model survives to fight another day…
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In the Dark 